1. Field of the Invention
The present invention relates to a parallelized power supply system, and more particularly to a parallelized power supply system suitable for use with AC-DC switching regulator power supplies which supply one or a plurality of d.c. powers to an apparatus whose uninterrupted operation is indispensable, such as an external storage device of a computer system.
Controls of parallelized power supplies are disclosed in "Load-Current-Sharing control for Parallel Operation of DC-to-DC Converters", by R. Wu et al., IEEE PESC-1993, pp. 101-107, "PARALLEL IDENTICAL DIRECT-MODE DC-DC CONVERTERS", by D. Azzis, et al., IBM Technical Disclosure Bulletin, Vol. 25, No. 2, July 1982, pp. 624-625, and JP-A-2-72638 (U). An operational amplifier relevant to this application is disclosed in LinCMOS .mu.POWER PRECISION QUAD OPERATIONAL AMPLIFIER TLC1079, TEXAS INSTRUMENTS, 1992, pp. 2-779 to 2-794.
2. Description of the Related Art
A conventional parallelized power supply system is associated with the following problems, from the viewpoint of satisfying the requirements by recent apparatuses such as uninterrupted operation of power supplies, live wire insertion/dismount of an AC-DC switching power supply (one or more power supplies among a plurality of power supplies under operation are replaced for the maintenance or because of defects without stopping the other power supplies), and downsizing (high performance with compact size).
Conventionally, a switch and a cable of a commercial a.c. power supply connected to AC-DC switching regulator power supplies or switching power supplies are positioned on the maintenance side, e.g., on a side panel or back panel of the apparatus. Therefore, a maintenance person can easily access these switch and cable, and the switching regulator power supplies may be inadvertently turned off.
Still further, switching power supplies for the same d.c. output voltage are run in parallel for the purpose of uninterrupted operation so that the total number of switching power supplies increases. The total amount of rush current flowing through the switching power supplies may flow through the commercial a.c. power supply at the worst. This too large rush current may break the commercial a.c. power supply facilities connected to the apparatus, and the operation of the apparatus may eventually be stopped.
In a conventional control of power supply voltage detection, two positive and negative d.c. power supplies are required in order to drive an operational amplifier used in a current detector circuit. Power for driving these two power supplies and power for driving loads are supplied from the same power supply system. Therefore, the power supply system is difficult to be made compact because of these two positive and negative d.c. power supplies.